Copending U.S. patent application Ser. No. 972,055 (A. R. Hartman-R. S. Scott-P. W. Shackle) discloses a prior invented solid-state protection circuitry comprising the combination of a gated diode switch, a zener diode, a resistor, and a capacitor. This circuitry is capable of providing voltage overload protection against voltage surges of one polarity of several hundred volts and at least several amperes and is relatively insensitive to changes in voltage with respect to time (dv/dt) until the magnitude of the voltage reaches a preselected level.
There have recently become available new forms of solid-state switches which can be operated at high voltages and at high currents. Switches of this kind are disclosed in U.S. patent application Ser. Nos. 972,056 (A. R. Hartman-T. J. Riley-P. W. Shackle), 971,886 (A. R. Hartman-B. T. Murphy-T. J. Riley-P. W. Shackle), and 972,021 (A. R. Hartman-A. U. Mac Rae-P. W. Shackle).
It is desirable to have solid-state circuitry which has the features of the above-described circuitry but which, in addition, is capable of providing protection against voltage surges of either polarity.